Method of making friction elements



Patented Feb. 26, 1935 I PATEN OFF-ICE V 1,993,601 I v I METHOD or MAKING FRICTION ELEMENTS v p it A. Blume, Detroit, Mich assignor to American'Brakeblok Corporation, vNew York; N. Y., a. corporatio n of N y 'L No Drawing. Original. application January 4 5, I 1931, Serial No. 506,752. Divided and this ap- -plication April 16, 1932, Serial l lo. 605,782 7 3 Claims. (o1-. 18 47.5)

This application is a division of my application SerialNo. 506,752, filed January 5, 1931.

This invention relates to the method of making composition friction elements and its ob- 5 ject is to provide a novel friction element which is fiexible and tough, which is wear and heat resistant and which can be readily and easily prepared and formed to shapes for brakes, clutches and other mechanical devices wherein a braking or retarding eifect is required.

It is a specific object of the invention to make a friction element in .strip form which has sufficient flexibility and transverse strength to enable it to be readily conformed and applied to arcuate or other supports therefor in brakes, clutches and the like and which is dense and hard and possesses desired friction qualities.

In the practice of my invention I provide a base mixture of short fiber asbestos, finely divided natural pyrobituminous material, to which sulfur and slaked lime may be added, and mix the same thoroughly in a dough mixer or other suitable apparatus. I also provide a bond mixture of vegetable drying oil, such as linseed oil, purely polymerized, that is, containing substantially no oxidized oil,.and a solvent or thinnerand add this bond mixture to the base mixturein the mixer and agitate the mass until the bond mixture is thoroughly incorporated in the base mixture. The resulting composition is then molded in a continuousstrip of desired dimensions and the strip is formed in a coil or cut into lengths and the coil or lengths are placed in a suitable oven and cured. A mixture which I have 0 used comprises short fiber asbestos 65 pounds; finely divided bituminous coal 25 pounds; sulfur 3 pounds; slaked lime 2 pounds; purely polymerized linseed oil 15 pounds; and oleum spirits 7 pounds. I use a purely polymerized linseed oil which has an acid No. 2.5. Whereas, ordinarily, linseed oil raw or double boiled becomes hard, dry and brittle in curing, purely polymerized linseed oil becomes tough, elastic and flexible in curing, and for these reasons it is highly desirable in the manufacture of composition friction elements because it imparts these qualities to the elements and provides a strong, tough element having desired tensile 50 and cross-sectional strength and sufiicient flexibility to enable it to be readily adapted for different installations. The purely polymerized linseed oil is sticky, gummy and of the consistency of heavy molasses and. I find it desirable to cut the oil with a suitable solvent or thinner to a consistency which will. permit it-v to. be readily. mixedfwith the base mixture}? w I i The coils or cut lengths of strip material are placed in an oven and are subjected toa cur- I ing temperature of from F. to 200 F. for a 5 sufiicientlength of time, depending upon the thickness of the material, to drive off the volatile matter, and then the temperature is stepped up to from 250 F. to 350 F. and maintaineduntil the curing is completed. This curing opera- 10 tion is conducted Without pressure and may continue from 8 to 15 hours.

The low acid value of the purely polymerized oil insures a low free fatty acid content. The slaked lime under heat supplied in the. curing 1 operation saponifies more or less of the free fatty acid content andproducesa form of soap which remains in the product as a latent lubricant. Under the heat of braking friction this soap produces a'slightlubricant effect which helps to prevent scoring or other destructive action of the brake element upon the brake drum or other part to be braked. I The slaked lime has the further quality of preventing shrinkage and warpage in curing, to a large extent. The sulfur assistsin maintaining the desired flexible quality of the element by causing the purely polymerized oil to dry to a tough elastic film in' a shorter time and at a lower temperature.

My invention provides a friction element which is particularly useful in brakes andclutches and which may be used for many other purposes. It is solid and hard, but not rigid, and it has sufficient flexibility to enable it to be easily fitted to arcuate or other supports for which it is 35 adapted without liability of fracturing the composition body, which would tend to promote disintegration and lessen the efficiency and life of the element. While I believe the invention will be used principally in the manufacture of friction elements in the form of strips, it canv also be used in the manufacture of friction elements in the form of blocks in a mold press and it will 1. The herein described method of making 55 the point of destruction of the molecular con:

stitution of ,theoil and for a period of time sufiicient to set the bond and without inducingjside reactions such as oxidation.

2. The herein described.,method} of making friction elements which consists in preparing .a

base mixture including a fibrous material and finely divided natural pyrobituminous material,

mixing the base mixture with a bondof veg'e--- table drying oil purely polymerized, that is, containing substantially no oxidized oil and not.

and without inducing side reactions such as 20 otherwise chemically changed, forming the resulting composition into shapes, and then cur-.

ing the shapes by subjecting them to heat in the presence of air and without pressure at a temperature below the point of destruction of the molecular constitution of the oil and for a period of time suflicient to set the bond and without inducing side reactions such as oxidation.

3. The herein described method of making friction elements which con sists in preparing a basemixture including 65 pounds of asbestos and 25 pounds of finely divided pyrobituminous 'materi'al', mixing with the base mixture a bond of 15 pounds of vegetable drying oil purely polymerized, that is, containing substantially no oxidizedfoil-and not otherwise chemically changed, forming the resulting composition into shapes, andthen curing the shapes-by subjecting them to, heat in the presence of air and without pres- "sureat-a temperature below the point of destruction of the molecular constitution of the oil andfor a period of time sufiicient to set the bond oxidation. r Y

' WILLIAM A. BLUlVIE. 

